The kinetics of fusion/fission of micelles, in the transition range between spherical and elongated micelles, has been investigated using an approach similar to those of Aniansson and Kahlweit. On the assumption that the relaxation process associated with the exchange of surfactant between micelles acid solution is very fast and that the creation of large aggregates by stepwise association of monomeric surfactants is slow, the frequency of relaxation was found to depend on the average collision frequency, the micelle length distribution, and the number density of micelles. Well above the cmc, the relaxation frequency is equal to the ratio of the average fusion rate over the derivative of the aggregate number with respect to the number of surfactant molecules in micelles. The obtained expression applies to many length distributions from short micelles with a low or a large polydispersity to elongated micelles. Numerical simulations of the variation of the relaxation frequency with surfactant concentration are given for three different micellar energy distributions.